A Hollywood Ending

Stunt Pilots To Capture Capsule Of Space Particles For Nasa.stunt Pilots To Capture Capsule Of Space Particles For Nasa

July 11, 2004|By Melissa Sanford The New York Times

SALT LAKE CITY — The 2-million-mile mission is nearly done, but its most perilous phase is yet to come.

Three years ago, NASA launched a robotic spacecraft, Genesis, from Kennedy Space Center. Since then, it has ranged far into space to collect samples of particles ejected from the surface of the sun. The mission is to end on Sept. 8, when the spacecraft releases a capsule containing the solar particles.

The capsule will float to Earth with a parachute, to be captured in midair by helicopters flown over the West Desert in Utah. Flying the helicopters will be two Hollywood stunt pilots hired by NASA.

The maneuver is more than 99 percent likely to be a success, said Dr. Donald S. Burnett, chief scientist for the project, but serious concerns remain. If it fails, the solar particles, which would be the first space samples delivered to Earth since 1972, could be damaged as the capsule hits ground.

"There is not a lot of margin for error," said Dan Rudert, one of the stunt pilots, who flew in The Hulk and S.W.A.T. "If we are too high, we either miss it altogether or we tear the chute. If we are too low, we'll catch the parachute on the skids, and then we could crash."

At $260 million, Genesis is part of a new generation of relatively inexpensive missions in which robotic spacecraft collect samples from space and return them for study. It flew to a spot 930,000 miles from Earth called the L1 Lagrangian Point, where the gravitational and centrifugal forces of the Earth and the sun balance, allowing the spacecraft to collect the solar particles without needing much rocket power to maintain its orbit. Understanding the composition of the particles will help explain how planetary objects formed, said Burnett, a geochemist at the California Institute of Technology.

On the Apollo missions, astronauts carried 840 pounds of moon rocks to Earth. The Genesis sample is significantly smaller, weighing only as much as a few grains of sand.

NASA scientists took extraordinary measures to keep the solar particles uncontaminated. The spacecraft collected them on wafers made of ultrapure materials like gold, sapphire and diamonds; the wafers are stored in a sterile container.

To ensure that the particles would remain attached to the wafers upon landing, the scientists devised a gentle landing method. They feared that even if the capsule floated to Earth on a parachute, the samples might be damaged when it hit the ground. So they came up with the idea of a midair retrieval.

"It will be a blow if we do not catch this," Burnett said. "We will still be able to recover some of the materials, but we would end up with a lot of things broken and damaged. We would spend a long time sorting through the materials."

When the capsule splits from the spacecraft, the Genesis will go into a long-term orbit around the sun while the capsule enters Earth's atmosphere at 24,700 miles per hour. To slow down the capsule's descent, a parachute is to open 19 miles above the ground. Then, a mile and a half from the ground, a larger parachute, called a parafoil, will open.

When the capsule slows to 23 miles per hour, a lead helicopter and a chase helicopter will use 18-foot poles with hooks on their ends to snare the parafoil. If they succeed, the fabric of the parafoil will collapse and hang with the capsule below. The pilots will then lower the capsule gently into a container on the ground.

"It should be a smooth and relatively precise maneuver, kind of like ballet," Rudert said. "But if the chute does not open completely, we are going to have to do some much more aggressive flying than we planned for."

NASA officials selected Hollywood stunt pilots for the job because they are experts at precision flying and what is called long-line work, Rudert said. Long-line pilots guide both their helicopters and loads dangling below them.

In Hollywood, Rudert, 45, flies with expensive cameras attached to the outside of his helicopter. But even so, this project is a new challenge.

In April, Rudert and the other pilot, Cliff Fleming, 54, completed five dress rehearsals of the catch over military sites in the West Desert and at Yuma, Ariz. The pilots retrieved the test object each time.

But no matter how much they practice, the pilots cannot control one critical variable, the weather. If it is too windy, helicopters cannot fly. If it is too foggy or rainy, the pilots will not be able to see the capsule.

At first, NASA scientists planned that in case of uncooperative weather they would keep the capsule in the spacecraft, return Genesis to orbit and try the sequence again in six months. But they recently decided to carry out the catch whatever the weather, Burnett said.

The reason is that the decision to return to orbit has to be made eight hours before the catch, and in an admission of the limits of science, the scientists said they could not reliably predict weather conditions that far in advance.